This invention relates to an enclosed-type magnetic disc recording and/or reproducing apparatus capable of preventing the lubricant from being introduced from bearing unit into the enclosed chamber by rotation of the magnetic disc and the flange driven within the enclosed chamber.
Generally, in magnetic disc recording and/or reproducing apparatuses, the magnetic head at operation usually operates while floating with a prescribed width of gap left between such head and the surface of the magnetic disc by existence of a substantially fixed thickness of thin air flow produced over the magnetic disc.
If lubricants, such as oil and grease, or other foreign matters stick to the magnetic disc and the magnetic head, the width of the aforesaid gap will become smaller than the prescribed level and, in an extreme case, the rotation of the magnetic disc will be retarded, causing the performance of the apparatus to be reduced. Though there had conventionally been proposed supply of clean air to the periphery of the magnetic head in order to avoid the above unfavorable state of things, it could not lead to a satisfactory result. The reason for this is that when the magnetic disc rotates, the air within the magnetic disc cover (hereinafter referred to as disc cover) covering the magnetic disc is subjected to a flow, thereby causing differences of air pressure with locations within the disc cover. Additionally, the pressure between the flange, fixed to the tip end of a shaft supported by the bearing unit provided at a base of the apparatus and fitted with the magnetic disc, and the base becomes lower than the atmospheric pressure, thereby vaporizing the lubricant, such as oil or grease, applied to the bearing member and causing it to be sucked into the disc cover. Thus, the vaporized lubricant spreads in all directions within the disc cover following the aforesaid air flow, sticking to the magnetic head, magnetic disc, and all other portions within the disc cover. Consequently, the life of the magnetic head and disc, as well as the capability of recording and/or reproducing data for the magnetic disc, may be reduced to cause malfunction.